(1) Field of the Invention
The present invention relates to mower safety blades and the method of making them, and is concerned primarily with a blade having a layer of high strength fabric in a homogeneous body of elastomeric material and plastic fibers. The blade has a centrally positioned metallic bar encased in the elastomeric material which bar does not extend to the ends of the blade. The outer portions of each blade has a cutting edge which intersects the fabric.
(2) Description of the Prior Art
In the U.S. Pat. No. 3,911,652, dated Oct. 14, 1975, there is disclosed a safety blade for rotary lawn mowers. U.S. Pat. No. 3,911,652 is believed to be the most relevant prior art. This patent discloses a blade having a central section and end portions. A pair of metallic bars are included in the central section and a body of rubber-like bonding material and layers of fabric are bonded about the metallic bars and extend through the end portions. Each of the end portions is formed with a cutting edge.
Safety mower blades must have the ability to resist elongation because of the high rpms at which they are used which is normally around 3600 rpm. The blades must have a long useful life comparable to that of a metallic rotary blade which means they must resist wear. The blade must also resist forces applied to it when cutting grass, for example, which tend to deflect the blade from its normal plane of rotation so that it will cut grass evenly. Since they are generally powered by gasoline motors, the temperature in the immediate vicinity of the blades can easily reach 150.degree. F. so that the materials used must not be adversely affected by such temperatures.
The safety blade of U.S. Pat. No. 3,911,652 solves the above identified problems by using multiple layers of fabric, four in the end portion, two in the central portion, plus two layers of metal, all of which are encased in a body of vulcanized rubber.